The association between Reichardt's ET-30 dye and amine- and carboxylate-terminated polyamido amine (PAMAM) dendrimers was investigated and shown to be different from results reported for micelles and traditional polymers. The absorption spectra illustrated that the solvatochromic, microenvironmental polarity probe associated with PAMAM dendrimers in less polar regions with a polarity comparable to 1-decanol. Model compounds that mimic PAMAMs' surface groups and branching moieties were used to better define the associated dye's location and demonstrated that ET-30 penetrated beyond the dendrimer's surface groups, into the interfacial region. Additionally, changing sample preparation methods controlled the nature and extent of the dye/dendrimer association. Under certain experimental conditions, the dye/dendrimer complexes formed large aggregates.
Dana L. Richter-Egger, Hong Li, and Sheryl A. Tucker, "Spectroscopic Investigations of Polyamido Amine Starburst Dendrimers with Reichardt’s ET-30 Dye," Appl. Spectrosc. 54, 1151-1156 (2000)